The cost in terms of both time and money of repairing aircraft wheel assemblies which have been damaged in storage or in transport adds significantly to total maintenance costs. Rough handling, for example, often leads to denting, gouging and other damage to the wheel or tire structure. This occurs with expensive frequency when the wheels are handled for shipment between airports. In order to detect and repair the possible damage, expensive and time-consuming operations such as X-ray inspection and repolishing must be employed. In some cases, damage to the sidewalls of the tire by a fork lift truck, for example, has required replacement of the tire.
The likelihood of loss or damage is further increased when the wheels are to be stored or shipped with bearings in place around the central hub of the wheel. In these cases, mishandling of the wheel assembly may lead to the bearings falling out or being damaged in transit. Mishandling is, however, not the only cause of otherwise unnecessary maintenance of aircraft wheel assemblies.
If wheel assemblies are shipped with insufficient covering, there is also the problem that dust, rain, condensation, etc., will have to be cleaned from the wheel or bearings before the assembly is fit for use. There has therefore been a long-standing need for some form of protective covering for aircraft wheel assemblies which not only lessens the risk of mechanical damage and loss, but also provides protection against the weather and against soiling.
Common ways of providing this covering illustrate the extent of the need, and the insufficiency of most prior solutions. Many airlines, for example, simply tape over the hub area of the wheel; some screw a special metal plate onto the hub in an attempt to hold in the wheel bearings; still others tape or strap often ill-fitting sheets of wood over the metal of the wheel. None of these prior solutions, however, provides the degree of protection and ease of installation which are desired in the airline industry.
A protector for aircraft wheel assemblies which has met the need to a much greater extent, and which consequently has enjoyed far greater success in the industry, is described in U.S. Pat. No. 4,304,279. According to this solution, an annular, mainly concave plastic cover is provided for each side of the wheel. The covers are positioned so that they cover the metal of the wheel, whereby an inwardly projecting annular protrusion on each cover seats about the tire bead on either side of the wheel in order to provide at least a partial weather seal. An inner annular recess on the outer cover is provided to receive the outer portion of a heat shield, which is often included in aircraft wheel assemblies. The covers are mounted on the wheel assembly, and are secured to each other, using a locking T-bar which is inserted through a central hole in the inner cover, through the central bore of the wheel, and lastly through a central hole in the outer cover. The T-bar is then rotated so that a T-member on the T-bar comes to rest in a radial groove in the outer member. Finally, a wing nut is used to tighten the covers.
This solution represents a marked improvement over the other prior art protectors, and is now used by a large number of the major air carriers of the world. It does, however, suffer from several weaknesses. In order to insure that the outermost portion of the T-bar does not extend beyond the outer limiting plane of either cover, T-bars of different lengths are needed for wheels of different thicknesses. It furthermore exhibits disadvantages, explained below, which are common to all arrangements according to the prior art.
A serious shortcoming of prior art arrangements is that they require wheel assemblies to be stored and moved mainly vertically. It is not possible to stack wheel assemblies horizontally, either in a storage area, or in the hold of an aircraft, since no part of the protectors adequately supports and protects protruding members of the wheel assembly. When positioned horizontally, there is furthermore a risk that bearings may become dislodged or even fall out. Because of these risks of potential damage, wheel assemblies according to prior art arrangements must be stored and moved mainly vertically, often in vertical, rollable stands or racks. Occasionally, the wheel assemblies are simply leaned either against each other or against some vertical supporting surface. There are at least two major drawbacks to this solution.
First is the danger of personal injury to the workmen who must handle the wheel assemblies. It is to be noted that most aircraft wheel assemblies weigh several hundred pounds each. In addition to the risk of injury, moving such a heavy wheel by hand often requires the efforts of more than one man. Ideally it should be possible to move at least one, and preferably more than one, wheel assembly using a forklift. This is, however, not possible using prior wheel protectors, since the wheels would have to be carried and stacked horizontally.
Second is the inefficient use of storage space associated with vertical storage. Short of installing special, heavy-duty shelves and loading ramps in the storage area, potential storage space higher than the diameter of a tire cannot be used. Vertical storage of course leads to a corresponding inefficient use of the cargo hold of an aircraft when transporting the wheel assemblies. It has been estimated that horizontal storage of typical aircraft wheel assemblies by stacking them three or four high reduces required storage space 40-50%.
U.S. Pat. No. 4,790,430 discloses a horizontally stackable shipping container including covers which are clamped on either side of an aircraft brake assembly. The containers are made stackable by providing the base and top covers with mating projections and recesses. The pattern and shape of the projections and recesses is, however, irregular, so that manufacture is unnecessarily complicated. The container disclosed is, moreover, limited to brake assemblies, and requires the brake assemblies to be removed and placed in a cylindrical body tube. The container is therefore not suitable or intended to allow quick mounting on entire aircraft wheel assemblies, and it cannot protect tires. Finally, the base and top covers are mainly flat, so that when stacked, there is little or no space between them. It is therefore not possible to remove, for example, the uppermost container using a forklift.
Accordingly, one object of the present invention is to provide an easily installed, light-weight, compact protector for wheel assemblies which seals effectively against the environment while providing improved protection against damage to not only the metal of the wheel but also to the tire. Another object is to provide adequate protection for bearings and, if mounted, protruding members such as a heat shield or brake lugs. Yet another object of the present invention is to provide a protector for wheel assemblies which permits stable horizontal stacking, storage and transportation of the assemblies.